JP6107951B2 - Base station apparatus, radio communication system, inter-cell interference control method, and program - Google Patents

Description

The present invention relates to a base station apparatus, a wireless communication system, an inter-cell interference control method, and a program .

  In recent mobile communication systems, it is necessary to cope with traffic that is increasing rapidly with the spread of smartphones. Under such circumstances, a heterogeneous network (HetNet: Heterogeneous Network) in which small cells are redundantly installed in the service area of a macro cell is attracting attention as a measure for increasing the communication capacity of the system. In HetNet, the throughput of the entire system can be improved by offloading communication traffic of user terminals (UE: User Equipment) in the area of the macro cell to a small cell.

  However, when the HetNet is configured with the same carrier frequency for the macro cell and the small cell, the user terminal located near the boundary of the small cell receives strong interference from the macro cell, so that the communication quality is greatly deteriorated.

  As a countermeasure against such inter-cell interference problem, LTE (Long Term Evolution), which is being discussed in 3GPP (3rd Generation Partnership Project), introduces a technology called eICIC (enhanced Inter Cell Interference Coordination). (Non-Patent Document 1). In eICIC applied in the time domain, subframes are used in cooperation between different cells in accordance with an ABS (Almost Blank Subframe) pattern that changes in a fixed or semi-fixed manner. ABS is a subframe for reducing transmission power on a physical channel or stopping transmission of user data. An ABS of an aggressor cell (for example, a macro cell) that is a cell that gives interference is used to protect resources in a subframe of a victim cell (for example, a small cell) that is a cell that receives interference. That is, in the small cell, user throughput and cell throughput can be improved by preferentially allocating a user with poor communication quality to the ABS time section of the macro cell in user selection in the scheduling function.

  Thus, in order for a small cell to utilize the ABS of a surrounding macro cell, the small cell needs to know the ABS pattern of the surrounding macro cell. Generally, a small cell can know the ABS pattern of a surrounding macro cell through a message of an X2 protocol that is an interface between base station apparatuses (eNB: evolved Node B) (Non-patent Document 2).

3GPP TS 36.300 V10.9.0 (2012-12) "Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (Release 10)", 16.1.5 Inter -cell Interference Coordination (ICIC) 3GPP TS 36.423 V10.5.0 (2012-03) "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 application protocol (X2AP) (Release 10)", 8.3.1 Load Indication

  However, the background art described above has the following problems. That is, when the base station apparatus cannot acquire an ABS pattern for some reason using the X2 interface, the above-described technique for reducing interference between cells cannot be applied, and thus the user throughput and the cell throughput cannot be improved. As a typical example in which an ABS pattern cannot be acquired between base station apparatuses, communication between base station apparatuses can be performed between a macro cell and a small cell because a vendor that provides the base station apparatus differs between the macro cell and the small cell. There are cases where it is impossible.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a base station apparatus, a radio communication system, and an inter-cell capable of improving user throughput and cell throughput by reducing interference between cells. To provide an interference control method and program.

The first base station apparatus of the present invention,
A base station device that performs radio communication with a user terminal located in its own cell,
Based on feedback information received from the user terminal, an estimation unit that estimates an intermittent transmission pattern of neighboring cells of the own cell;
A scheduling unit configured to perform scheduling of the user terminal based on the intermittent transmission pattern.

The second wireless communication system of the present invention is
A wireless communication system comprising a user terminal and a base station device that performs wireless communication with the user terminal located in the own cell,
The user terminal includes a transmission unit that generates feedback information based on a reception result of data received from the base station apparatus and transmits the feedback information to the base station apparatus,
The base station apparatus, based on the feedback information received from the user terminal,
An estimation unit for estimating an intermittent transmission pattern of a neighboring cell of the own cell;
A scheduling unit configured to perform scheduling of the user terminal based on the intermittent transmission pattern.

The third inter-cell interference control method of the present invention is as follows.
Based on feedback information received from user terminals residing in the own cell, estimating an intermittent transmission pattern of neighboring cells of the own cell;
Scheduling the user terminal based on the intermittent transmission pattern.

A fourth program of the present invention,
On the computer,
A procedure for estimating an intermittent transmission pattern of a neighboring cell of the own cell based on feedback information received from a user terminal located in the own cell;
On the basis of the intermittent transmission pattern, the procedure for scheduling the user terminal, Ru is performed and.

According to the present invention, it is possible to provide a base station apparatus, a radio communication system, an inter-cell interference control method, and a program capable of improving user throughput and cell throughput by reducing interference between cells.

It is the figure which showed the structure of the radio | wireless communications system concerning 1st Embodiment. It is the sequence diagram which showed the operation | movement of the radio | wireless communications system concerning 1st Embodiment. It is the figure which showed the structure of the radio | wireless communications system concerning 2nd Embodiment. It is the figure which showed the structure of the radio | wireless frame used with the radio | wireless communications system concerning the system of 2nd Embodiment. It is the figure which showed the structure of eNB and UE concerning 2nd Embodiment. It is the figure which showed the relationship between the period of an ABS pattern, and the period of an accumulation period. It is the flowchart which showed operation | movement of eNB concerning 2nd Embodiment. It is a 1st figure for demonstrating the operation | movement of ABS determination. It is a 2nd figure for demonstrating the operation | movement of ABS determination. It is the figure which showed the structure of the modification of the radio | wireless communications system concerning 2nd Embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
(First embodiment)
[Constitution]
FIG. 1 is a diagram illustrating an example of a configuration of a wireless communication system according to the first embodiment. The base station apparatus 10 can perform wireless communication with the user terminal 20. Moreover, although not shown in figure, the base station apparatus 10 comprises a cell, and the adjacent cell which base station apparatuses other than a self-base station apparatus comprise exists in the periphery.

  The base station apparatus 10 includes an estimation unit 11 and a scheduling unit 12. In addition, the user terminal 20 includes a transmission unit 21. Note that, in FIG. 1, among the functional blocks included in the base station device 10 and the user terminal 20, only the components related to the present embodiment are shown. That is, the base station device 10 includes a functional block for causing the base station device 10 to function as a base station device, although not shown. Similarly, although not shown, the user terminal 20 includes functional blocks for causing the user terminal 20 to function as a user terminal.

  The estimation unit 11 estimates the intermittent transmission pattern used in the adjacent cell based on the feedback information received from the user terminal 20.

  The scheduling unit 12 schedules the user terminal 20 based on the intermittent transmission pattern estimated by the estimation unit 11.

  The transmission unit 21 of the user terminal 20 transmits feedback information generated according to the reception result of the data received from the base station device 10 to the base station device 10.

[Operation]
FIG. 2 is a sequence diagram illustrating an example of the operation of the wireless communication system according to the first embodiment. Hereinafter, the operations of the base station apparatus 10 and the user terminal 20 will be described with reference to FIG.

  First, the base station apparatus 10 transmits data to the user terminal 20 (step S11), and the user terminal 20 receives this (step S12).

  Next, the user terminal 20 generates feedback information based on the received data (step S13), and transmits this to the base station apparatus 10 (step S14). Here, the content of the feedback information is, for example, ACK (Acknowledge) when data is correctly received, and NACK (Negative AcKnowledge) when data is not correctly received. Note that the user terminal 20 does not transmit ACK or NACK when it cannot detect data transmission addressed to itself. Since these series of operations are general user terminal operations, the present invention can also be applied to existing user terminals.

  Then, the base station apparatus 10 estimates the intermittent transmission pattern used in the adjacent cell of the base station apparatus 10 based on the received feedback information (step S15). Here, the intermittent transmission pattern is a fixed interval between a time interval in which transmission power on a physical channel is reduced (including transmission stop) and a time interval without such restriction within a certain interval, Alternatively, it means an appearance pattern of those sections in one cycle when appropriately combined and repeated semi-fixedly. The ABS pattern described above can be said to be an example of an intermittent transmission pattern.

  A specific example of the operation for estimating the intermittent transmission pattern will be described. For example, a time interval in which a lot of NACK is included in the feedback information is a time interval in which the reception power at the user terminal 20 is determined to be low due to strong interference from adjacent cells, and transmission power is reduced (including transmission suspension). It is determined that it is not. On the other hand, a time interval in which many ACKs are included is a time interval in which the reception quality at the user terminal 20 is determined to be high because interference from adjacent cells is weak, and transmission power is reduced (including transmission suspension). judge.

  Next, the base station apparatus 10 performs scheduling of the user terminal 20 based on the estimated intermittent transmission pattern (step S16).

  The scheduling process includes, for example, a process in which the base station apparatus 10 selects a user terminal 20 that transmits data in a predetermined time interval, a process of selecting a radio parameter used when transmitting data, and a reception from the user terminal 20 Processing for retransmitting data to the user terminal 20 in accordance with the feedback information. Note that only a part of these processes may be executed without executing all of these processes.

  Here, the process in which the base station apparatus 10 selects the user terminal 20 that transmits data will be specifically described. In the time interval in which the transmission power is reduced (including the transmission stop) in the intermittent transmission pattern, there is a high possibility that the time interval has less interference from the adjacent cell. Therefore, the base station apparatus 10 is located near the boundary with the adjacent cell. The user terminal 20 that is located and has poor communication quality is selected. On the other hand, the base station apparatus 10 selects the user terminal 20 having normal communication quality in a time interval that is not a time interval in which transmission power is reduced (including transmission stop). In addition, when there is no data which the base station apparatus 10 should transmit, the base station apparatus 10 does not select any user terminal 20.

  An example of radio parameter selection will be specifically described. Examples of radio parameters include modulation schemes and coding rates. For example, in the selection of the modulation scheme, the base station apparatus 10 selects QPSK (Quadrature Phase Shift Keying) that has low transmission efficiency but high transmission error tolerance for the user terminal 20 with poor communication quality. On the other hand, the base station apparatus 10 can select 64QAM (Quadrature Amplitude Modulation) with low transmission error tolerance but high transmission efficiency for the user terminal 20 with good communication quality. Furthermore, as an example of the selection of the coding rate, the base station apparatus 10 selects a coding rate with a low coding rate with low transmission efficiency but high error tolerance for the user terminal 20 with poor communication quality, and the communication quality is low. For a good user terminal 20, a coding rate with a high coding rate with low error tolerance but high transmission efficiency is selected.

[effect]
The base station apparatus concerning this embodiment can estimate the intermittent transmission pattern of an adjacent cell, and can perform scheduling of a user terminal based on the estimated intermittent transmission pattern. Therefore, the base station apparatus selects a user terminal whose communication quality is deteriorated due to interference from an adjacent cell in a time interval in which the transmission power in the intermittent transmission pattern is reduced (including transmission stop). Parameters can be selected. As a result, it is possible to avoid degradation of the communication quality of the user terminal due to interference received from adjacent cells, and improve user throughput.

As described above, according to the present embodiment, a base station apparatus, a radio communication system, an inter-cell interference control method, and a program that can improve user throughput and cell throughput by reducing interference between cells. Can be provided.
(Second Embodiment)
The second embodiment is an example in which the present invention is applied to an LTE mobile communication system of FDD (Frequency Division Duplex).

[Constitution]
FIG. 3 is a diagram illustrating a configuration example of a wireless communication system according to the second embodiment. The eNB 100 is a base station of the small cell 400, and performs wireless communication with the UE 200 located in the cell. Note that the UE 200 is not limited to one, and a plurality of UEs 200 may exist. The eNB 300 is a base station of the macro cell 500. The macro cell 500 and the small cell 400 form a HetNet with overlapping cover areas. The small cell 400 and the macro cell 500 are adjacent to each other. When the small cell 400 and the macro cell 500 use the same carrier frequency, the UE 200 receives interference from the macro cell 500. Note that the number of small cells 400 present in the cover area of the macro cell 500 is not limited to one. Since this embodiment is an operation closed to the eNB 400, the number of small cells is not affected.

  FIG. 4 is a diagram illustrating a configuration example of a radio frame used in the radio communication system according to the present embodiment. Referring to FIG. 4, wireless communication is performed based on 1024 wireless frames to which numbers 0 to 1023 called SFN (System Frame Number) are assigned on the time axis. Further, one radio frame is divided into 10 subframes with numbers 0 to 9. Wireless communication is performed in units of this subframe. FIG. 4 also shows the relationship between such a radio frame and an ABS pattern repeated at a predetermined cycle. In the example of FIG. 4, the ABS pattern has four radio frames, that is, the period is 40 ms. In the LTE wireless communication system, the period of the ABS pattern is always 40 ms in FDD. On the other hand, TDD (Time Division Duplex) is 20 ms, 60 ms, or 70 ms depending on the time division pattern. In TDD, a macro cell and a small cell constituting HetNet use the same time division pattern. Thus, since the period of the ABS pattern is uniquely determined according to the cell configuration, the eNB can know the period of the ABS pattern applied to the macro cell from its configuration information.

If the i-th subframe in the ABS pattern period is SFN = n (n = 0, 1, 2,...) And subframe = m (m = 0, 1, 2,...),
i = mod (n, 4) * 10 + m; (0 ≦ i <39)
It can be expressed as. Here, mod (n, 4) indicates a remainder obtained by dividing n by 4. Note that the starting point of the ABS pattern estimated by the small cell may deviate from SFN = 0 and subframe0. In this case, as shown below, C (C = 0, 1, 2,...) Representing a subframe shift may be added to the right side of the above equation.

i = mod (mod (n, 4) * 10 + m + C, 40); (0 ≦ i <39)
FIG. 5 is a diagram illustrating configurations of the eNB 100 and the UE 200 according to the present embodiment. Note that, in FIG. 5, among the functional blocks included in the eNB 100 and the UE 200, only components that are particularly related to the present embodiment are illustrated. That is, although not shown, the eNB 100 includes functional blocks for causing the eNB 100 to function as an eNB. Similarly, although not shown, UE 200 includes a functional block for causing UE 200 to function as a UE.

  The eNB 100 includes a reception unit 110, an ABS pattern estimation unit 120, a scheduler 130, and a transmission unit 140. More specifically, the ABS pattern estimation unit 120 includes a feedback information counter 121, a memory 122, and an ABS determination unit 123.

  The receiving unit 110 receives feedback information from the UE 200. The details of the feedback information are the same as in the first embodiment.

  The ABS pattern estimation unit 120 estimates an ABS pattern based on the feedback information.

  The feedback information counter 121 counts the number of feedback information received for each subframe number i during the accumulation period together with the memory 122, and stores this in the memory 122.

  The memory 122 has N areas from 0 to N-1. Here, N is equal to the number of subframes included in one period of the ABS pattern, and N = 40 in the example of FIG. In the memory area #i (0 ≦ i <N), various information in the i-th (counted from 0) subframe in one cycle of the ABS pattern is stored. The information stored here is, for example, the following four pieces of information.

(A) The total number of initial transmission data in the #i subframe group within the accumulation period (hereinafter, the cumulative number of transmission data),
(B) The total number of NACKs received for the initial transmission data in the #i subframe group within the accumulation period (hereinafter, the NACK accumulation number),
(C) Error rate in the subframe group of #i within the accumulation period (D) ABS determination result in the subframe group of #i within the accumulation period Here, the accumulation period is a period sufficiently longer than the period of the ABS pattern. For example, as shown in FIG. 6, the period is an integral multiple of the period of the ABS pattern. The transmission data here corresponds to a transport block in a 3GPP system, for example. (B) is counted by the feedback information counter 121.

  The ABS determination unit 123 calculates an error rate in the i-th subframe based on the transmission data accumulation number and the NACK accumulation number stored in the memory 122, and writes the calculated result in the memory area #i of the memory 122. Further, based on the error rate, it is determined whether or not the i-th subframe is an ABS, and the ABS determination result is written in the memory area #i of the memory 122.

  The scheduler 130 performs scheduling of the UE 200 based on the ABS pattern estimated by the ABS pattern estimation unit 120.

  The transmission unit 140 transmits user data and control information necessary for demodulation of the user data to the user terminal selected by the scheduler 130 using the resource selected by the scheduler 130. In addition, transmission of control information may be omitted when transmitting user data, such as SPS (Semi-Persistent Scheduling) defined in the specifications of the 3GPP LTE system.

  The UE 200 includes a reception unit 210, a feedback information generation unit 220, and a transmission unit 230. The receiving unit 210 receives user data and control information transmitted by the eNB 100. The feedback information generation unit 220 generates feedback information according to whether or not user data has been successfully received. The transmission unit 230 transmits the generated feedback information to the eNB 100.

[Operation]
FIG. 7 is a flowchart illustrating an example of an operation of the eNB 100 (ie, a small cell base station) according to the second embodiment. Hereinafter, the operation of the eNB 100 in the i-th subframe (SFN = n, subframe = m) in the ABS pattern period will be described with reference to FIG.

  First, when processing is started (step S101), the scheduler 130 confirms the ABS pattern (step S102). More specifically, by referring to the information of the ABS determination result of the memory area #i of the memory 122, it is confirmed whether or not the subframe is an ABS.

  Next, the scheduler 130 selects a user communicating with the subframe according to whether the subframe is ABS or not, and selects a radio parameter used by the user (step S103). The operation of the scheduler is the same as in the first embodiment.

  Subsequently, the transmission unit 140 transmits data (user data and control information) using the selected wireless parameter to the user selected by the scheduler 130 in the subframe (step S104). The receiving unit 110 receives feedback information including ACK or NACK from the UE of each user who has received the data, and determines whether the feedback information is ACK or NACK (step S105).

  Next, the feedback information counter 121 counts the number of NACKs for the first transmission data from the NACKs determined by the receiving unit 110 (step S106). The transmission unit 140 counts the first transmission data from the number of user transmission data. Further, the transmission unit 140 and the feedback information counter 121 respectively update the transmission data accumulation number and the NACK accumulation number in the memory area #i corresponding to the subframe (step S107). The number of data transmissions may be counted by the scheduler unit 130. The number of NACKs counted here is feedback for user data transmitted in the i-th and previous subframes (in LTE FDD, feedback for data transmitted in the mod (i-4, 40) -th subframe is subframe #i). Received). This time difference may be taken into account when calculating the error rate, or the NACK accumulated number may be stored in the memory area mod (i−4, 40).

  Next, the ABS determination unit 123 determines whether it is the last update timing in the accumulation period (step S108). More specifically, the ABS determination unit 123 determines that it is the last update timing when the subframe is in one cycle of the last ABS pattern in one cycle of the accumulation period illustrated in FIG. As a result of the determination, if it is not the last update timing (step S108 NO), the processing in the subframe is terminated (step S112). If it is the last update timing (step S108 YES), the error rate in the memory area #i is calculated (step S109). Subsequently, the ABS determination unit 123 determines whether the subframe is an ABS according to the calculated error rate (step S110). The ABS determination method will be described later in detail. Thereafter, the ABS determination unit 123 clears the transmission data accumulation number and the NACK accumulation number in the memory area #i for the ABS determination in the period of the next accumulation period (step S111), and ends the subframe process. Step S112).

  Here, the operation of the scheduler 130 in this embodiment, particularly the ABS determination method in step S110 of FIG. 7, will be described in detail below.

  The scheduler 130 in this embodiment performs scheduling in consideration of the ABS pattern of the neighboring cell that causes interference with the own cell. In the specification of Release-10 of 3GPP, it is possible to make the UE perform measurement and feedback of radio quality by distinguishing between ABS and subframe that is not ABS. When the scheduler 130 selects a UE (that is, a user) that performs communication in a certain subframe, the scheduler 130 preferentially selects a UE having poor communication quality due to interference from adjacent cells in the subframe that is an ABS. select. On the other hand, in the subframe that is not an ABS, a UE located near the boundary of such a cell is avoided and another UE is selected.

  Further, the scheduler 130 selects an appropriate radio parameter so as to achieve the target error rate (target error rate). This operation will be described with reference to FIG. The figure shows an example of the error rate in the memory area #i in the memory 122. The scheduler 130 performs control so that the error rate calculated in step S109 does not exceed the range from the lower limit value PT− of the target error rate to the upper limit value PT + of the target error rate, thereby achieving the target error rate PT. To work. When the scheduler 130 can correctly recognize the ABS pattern of the adjacent cell, the error rate of the memory area #i converges to PT by the action of the scheduler 130. However, if the scheduler 130 has not correctly recognized the ABS pattern of the adjacent cell, the error rate of the memory area #i does not necessarily converge to PT as shown in FIG. The error rate in this case corresponds to one of the following three cases.

Case 1: Value between PT− and PT + (memory area # 1 in FIG. 9)
Case 2: A value higher than PT + (memory areas # 0, # 2, # N-1 in FIG. 9)
Case 3: A value lower than PT- (memory area # 3 in FIG. 9)
In the ABS determination (step S110), it is determined for each of these cases whether or not it is an ABS as follows.

  In the subframe corresponding to the memory area classified as case 1, it is determined that the error rate can be controlled as expected by the scheduler 130. Therefore, the recognition of the ABS pattern in the scheduler 130 matches the ABS pattern of the adjacent cell. Judge that Therefore, the previous determination result is maintained in the ABS determination in the subframe.

  In the subframe corresponding to the memory area classified as case 2, it is determined that the error rate is higher than the target value, the reception quality at the UE 200 is worse than the assumption of the scheduler 130, that is, the interference from the adjacent cell is strong. Here, the reception quality means, for example, SINR (Signal to Interference and Noise power Ratio). In such a case, the eNB 100 is required to retransmit data to the UE 200, so that radio resources are wasted, and the maximum throughput cannot be achieved. In the ABS determination, it is determined that the subframe is not set to ABS in the adjacent cell, and the determination result is not ABS.

  In the subframe corresponding to the memory area classified as case 3, since the error rate is too lower than the target value, it is determined that the reception quality at the UE is better than that assumed by the scheduler, that is, the interference from adjacent cells is weak. In this case, originally, radio parameters with higher transmission efficiency (for example, higher coding rate) should have been used, and radio resources are wasted as in the case 2, so that the maximum throughput can be reduced. Cannot be achieved. In the ABS determination, it is determined that the subframe is set to ABS in the adjacent cell, and the determination result is assumed to be ABS.

[effect]
According to the invention of the present embodiment, even when the eNB cannot obtain the information of the ABS pattern of the neighboring cell from another device, the eNB estimates the ABS pattern based on the estimated ABS pattern. Scheduling can be performed. Therefore, the scheduler can improve the user throughput of the UE by preferentially selecting a UE that is located in the vicinity of the cell boundary and is susceptible to interference from adjacent cells in the ABS time interval.

Also, UEs after 3GPP Release-10 can perform feedback by distinguishing between ABS and non-ABS subframes. Therefore, if the invention according to the present embodiment is applied to an eNB that supports 3GPP Release-10, the scheduler of the eNB can select an optimal radio parameter for the UE in each subframe of ABS and non-ABS. As a result, it is possible to maximize user throughput and cell throughput.
(Modification of the embodiment)
In carrying out the present invention, various modifications can be considered, and the present invention is not limited to the above-described embodiment.

[Modification 1]
In the second embodiment, the period of the ABS pattern estimated by the ABS pattern estimator 120 is the same as the period (40 ms) of the ABS pattern of the adjacent cell, but this is the period of HARQ (Hybrid Automatic Repeat reQuest) (8 ms). It is good. In this case, the number of memory areas in the memory 122 is 8 instead of 40, and the memory area can be reduced. In addition, since the accumulation period can be shortened, there is an effect that it can be quickly followed by updating the ABS pattern. (Applicable for LTE FDD).

[Modification 2]
The following variations may be added to the ABS determination method in the ABS pattern estimation unit 120. That is, the feedback information counter 121 counts the number of ACK / NACK undetected that is determined by the receiving unit 110 to have failed to receive feedback information. The objects to be counted here are all transmission data for which control information is transmitted along with data transmission, and are not limited to initial transmission. The control information is information notified by PDCCH (Physical Downlink Control Channel) in 3GPP, for example. In this case, the information stored in the memory area #i of the memory 122 is replaced with the following four pieces of information.

(A) The total number of transmission data (hereinafter referred to as control information inclusion transmission data) transmitted with control information in the subframe group of #i within the accumulation period,
(B) The total number of cases where feedback information is not received from the UE for the control information inclusion transmission data in the subframe group of #i within the accumulation period (hereinafter, ACK / NACK not detected),
(C) Error rate of transmission data including control information in #i subframe group in accumulation period (D) ABS determination result in #i subframe group in accumulation period Note that the error rate here is ACK / It can be obtained by dividing the total number of NACK not detected by the total number of transmission data including control information.

  Since the UE does not transmit feedback information when the control information is incorrect and cannot be detected, ACK / NACK is not detected in the eNB. In this modification, it is possible to estimate the ABS pattern based on the error rate of the control information, not the error rate of the user data. In general, the scheduler selects radio parameters so that the error rate of the control information also satisfies the target error rate. For this reason, in the present modification, the configuration and operation other than the portion for calculating the error rate are the same as those in the second embodiment described above.

[Modification 3]
In the second embodiment, the ABS pattern is estimated based on the error rate obtained from the transmission data accumulation number and the NACK accumulation number in a predetermined subframe group within the accumulation period. The ABS pattern may be estimated based on statistics of the number of retransmissions in a predetermined subframe group within the accumulation period by modifying this. The eNB 100 retransmits the data when it cannot normally transmit data to the UE 200. Examples of cases where data transmission cannot be performed normally include a case where the eNB 100 receives a NACK from the UE 200 or a case where neither an ACK nor a NACK has been received. Note that the number of retransmissions may or may not include initial transmission.

  In this modification, the target error rate (PT) in the second embodiment is set to the expected value of the number of retransmissions, the upper limit (PT +) of the target error rate is set to the upper limit of the number of retransmissions, and the lower limit (PT−) of the target error rate is set. The ABS is determined by replacing the number with the lower limit of the number of retransmissions. Here, the expected value of the number of retransmissions can be calculated based on PT, the upper limit of the number of retransmissions can be calculated based on PT +, and the lower limit of the number of retransmissions can be calculated based on PT−. In the ABS determination in this case, when the number of retransmissions in the subframe group is a value in a range from the lower limit of the number of retransmissions to the upper limit of the number of retransmissions, the previous determination result is maintained. If the value is larger than the upper limit of the number of retransmissions, it is determined not to be ABS, and if the value is smaller than the lower limit of the number of retransmissions, it is determined to be ABS. In this case, it is not necessary to calculate the error rate using the cumulative number of transmission data when determining the ABS.

[Modification 4]
In the second embodiment, as illustrated in FIG. 3, the present invention has been described by taking as an example a case where a cell that receives interference from the macro cell 500 is one of the small cells 400. As shown in FIG. 10, the present invention can be applied to a case where there are a plurality of cells that receive interference from the macro cell 500 such as the small cells 710 and 810 as well as the small cell 400. This modification is a small cell connected to the same monitoring / control console 600, and all or some of the small cell base stations have an ABS pattern estimation function, and It is applicable to small cells whose timing is synchronized.

  The monitoring / control console 600 collects each ABS pattern estimated by the eNBs (100, 700, and 800) of each small cell having an ABS pattern estimation function, and performs ABS for each subframe of the collected ABS pattern. By taking the majority decision, it is possible to improve the ABS pattern estimation accuracy. In addition, the monitoring / control console 600 collects information on the transmission data accumulation number and the NACK accumulation number for each memory area from the eNB of each small cell, sums these, and calculates the error rate for each memory area. ABS determination may be performed based on the error rate. The monitoring / control console 600 informs the eNB of each small cell of the obtained ABS pattern estimation result. By doing so, the monitoring / control console 600 can obtain a statistically more reliable ABS pattern estimation result, and the eNB of each small cell can perform scheduling based on the highly accurate ABS pattern. As a result, user throughput and cell throughput can be further improved.

  In addition, the monitoring / control console 600 may collect the ABS pattern estimated by the eNB of the small cell that receives the strongest interference among the small cells, and notify the eNB of the other small cells of the ABS pattern. In this case, the processing amount of the monitoring / control console 600 may be smaller than that of the method in which the majority decision of the ABS determination result is made for each subframe.

  Furthermore, when not all eNBs of each small cell have an ABS pattern estimation function, the ABS pattern estimation results collected from the eNB having the estimation function are not provided with the estimation function. You may notify eNB. By doing so, it is possible to improve user throughput and cell throughput even in a cell configured by an eNB that does not have an ABS pattern estimation function.

  Note that the above base station apparatus and wireless communication system can be realized by hardware, software, or a combination thereof. The inter-cell interference control method performed by the base station apparatus and the radio communication system can also be realized by hardware, software, or a combination thereof. Here, “realized by software” means realized by a computer reading and executing a program.

The program can be stored and provided to a computer using various types of non-transitory computer readable media. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Compact Disc-Read Only Memory). , CD-R, CD-R / W, DVD-ROM (Digital Versatile Disc-ROM), DVD-R, DVD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM) ), Flash ROM, RAM (Random Access Memory)). The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.
While the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.
This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2013-141202 for which it applied on July 5, 2013, and takes in those the indications of all here.

10 base station apparatus 11 estimation unit 12 scheduling unit 20 user terminal 21 transmission unit 100, 300, 700, 800 eNB
DESCRIPTION OF SYMBOLS 110 Reception part 120 ABS pattern estimation part 121 Feedback information counter 122 Memory 123 ABS determination part 130 Scheduler 140 Transmission part 200 UE
210 Receiver 220 Feedback Information Generator 230 Transmitter 400, 710, 810 Small Cell 500 Macro Cell 600 Monitoring / Control Console

Claims (10)

A base station device that performs radio communication with a user terminal located in its own cell,
Based on feedback information received from the user terminal, an estimation unit that estimates an intermittent transmission pattern of neighboring cells of the own cell;
A base station apparatus comprising: a scheduling unit configured to perform scheduling of the user terminal based on the intermittent transmission pattern.   In the scheduling, the base station apparatus selects a user terminal to transmit data in a predetermined time interval, a process to select a radio parameter to be used for the transmission, and the user according to the feedback information The base station apparatus according to claim 1, comprising at least one of processes for retransmitting data to a terminal.   The estimation unit estimates the intermittent transmission pattern based on the number of NACKs received from the user terminal in each subframe group within a period of the intermittent transmission pattern in a predetermined cumulative period. Item 3. The base station apparatus according to Item 1 or 2.   The estimation unit estimates the intermittent transmission pattern based on the number of the feedback information that could not be detected in each subframe group within the period of the intermittent transmission pattern in a predetermined cumulative period. Item 3. The base station apparatus according to Item 1 or 2.   The estimation unit estimates the intermittent transmission pattern based on the number of times data is retransmitted to the user terminal in each subframe group within a period of the intermittent transmission pattern in a predetermined cumulative period. Item 3. The base station apparatus according to Item 1 or 2.   The base station apparatus according to claim 1, wherein a period of the intermittent transmission pattern estimated by the estimation unit is equal to a period of the intermittent transmission pattern of the adjacent cell.   The base station apparatus according to claim 1, wherein a period of the intermittent transmission pattern estimated by the estimation unit is equal to a period of HARQ (Hybrid Automatic Repeat reQuest). A wireless communication system comprising a user terminal and a base station device that performs wireless communication with the user terminal located in the own cell,
The user terminal includes a transmission unit that generates feedback information based on a reception result of data received from the base station apparatus and transmits the feedback information to the base station apparatus,
The base station apparatus, based on the feedback information received from the user terminal, an estimation unit that estimates an intermittent transmission pattern of an adjacent cell of the own cell;
A wireless communication system comprising: a scheduling unit configured to perform scheduling of the user terminal based on the intermittent transmission pattern. Based on feedback information received from user terminals residing in the own cell, estimating an intermittent transmission pattern of neighboring cells of the own cell;
And scheduling the user terminal based on the intermittent transmission pattern. On the computer,
A procedure for estimating an intermittent transmission pattern of a neighboring cell of the own cell based on feedback information received from a user terminal located in the own cell;
On the basis of the intermittent transmission pattern, the procedure for scheduling the user terminal, program for executing the city.

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